ComSonics Inc. 2007VMD Manual Do Utilizador
Qualifier X-Ray
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Qualifier X-Ray System Overview
The ComSonics Qualifier X-Ray System provides a method for identifying the
internal shielding integrity of the CATV network in a subscriber’s residence without
the need to enter the premises.
A test activation transmitter is located within the Qualifier Hand Held Device
(HHD). This transmitter provides a signal to the Qualifier Vehicle Mounted Device
(VMD) and sets up the HHD to measure levels of ingress from the VMD signal
appearing in the return upstream path.
With the HHD connected to the residential side of either the ground block or the
drop cable, a press of the HHD button activates the VMD to generate a brief 5-
watt signal pulse at a frequency, just above the CB radio band, within the up-
stream frequency spectrum.
The VMD test signal envelopes the residence with a level of about +58 dBmV
(assuming the service vehicle is about 75 feet from the residence). Shielding
flaws, within the residential cabling, allow the VMD signal to enter the return up-
stream path. The HHD detects the VMD test signal and displays a shielding integ-
rity value based on the ingress level measured.
The threshold setup function in the HHD determines the indication of PASS or
FAIL with the integrity measurement.
Shielding Integrity Measurement
The Qualifier X-Ray System utilizes a unique measurement method to determine
the relative shielding integrity of a customer premise without a need to enter the
structure. This method provides the user with a numeric display representing a
calculated shielding factor, in dB, of the premise under test.
The type of flexible coaxial cable used for drops and house wiring typically has a
shielding integrity factor in the range of 80 to 120 dB. But with the addition of con-
nectors, splitters, VCRs, televisions, PC modems, and other devices along with
improper installation techniques; the total overall shielding integrity can degrade
appreciably. The possibility of noise ingress (undesirable signals) increases
greatly if the shielding integrity is not sufficient. Noise ingress causes interference
with the return path signals and reduces the reliability of two-way signal communi-
cations.
The Qualifier X-Ray system enables the user to obtain a shielding integrity read-
ing in the range of 80 dB (very good) to 25 dB (very poor). Each measurement
reading includes a PASS or FAIL indication, based on a user selectable threshold
value, for easy measurement status determination. The threshold function can be
turned off.
Formula for calculating the shielding integrity reading:
The ComSonics Qualifier X-Ray System provides a method for identifying the
internal shielding integrity of the CATV network in a subscriber’s residence without
the need to enter the premises.
A test activation transmitter is located within the Qualifier Hand Held Device
(HHD). This transmitter provides a signal to the Qualifier Vehicle Mounted Device
(VMD) and sets up the HHD to measure levels of ingress from the VMD signal
appearing in the return upstream path.
With the HHD connected to the residential side of either the ground block or the
drop cable, a press of the HHD button activates the VMD to generate a brief 5-
watt signal pulse at a frequency, just above the CB radio band, within the up-
stream frequency spectrum.
The VMD test signal envelopes the residence with a level of about +58 dBmV
(assuming the service vehicle is about 75 feet from the residence). Shielding
flaws, within the residential cabling, allow the VMD signal to enter the return up-
stream path. The HHD detects the VMD test signal and displays a shielding integ-
rity value based on the ingress level measured.
The threshold setup function in the HHD determines the indication of PASS or
FAIL with the integrity measurement.
Shielding Integrity Measurement
The Qualifier X-Ray System utilizes a unique measurement method to determine
the relative shielding integrity of a customer premise without a need to enter the
structure. This method provides the user with a numeric display representing a
calculated shielding factor, in dB, of the premise under test.
The type of flexible coaxial cable used for drops and house wiring typically has a
shielding integrity factor in the range of 80 to 120 dB. But with the addition of con-
nectors, splitters, VCRs, televisions, PC modems, and other devices along with
improper installation techniques; the total overall shielding integrity can degrade
appreciably. The possibility of noise ingress (undesirable signals) increases
greatly if the shielding integrity is not sufficient. Noise ingress causes interference
with the return path signals and reduces the reliability of two-way signal communi-
cations.
The Qualifier X-Ray system enables the user to obtain a shielding integrity read-
ing in the range of 80 dB (very good) to 25 dB (very poor). Each measurement
reading includes a PASS or FAIL indication, based on a user selectable threshold
value, for easy measurement status determination. The threshold function can be
turned off.
Formula for calculating the shielding integrity reading:
D2I = Pmax [+85] - (antenna gain [2.5] + free space loss [25]) - measured value
*D2I is the acronym for Dwelling Ingress Integrity